On Jan 12, 2014, at 1:58 PM, Jean François Martinez <jfm...@free.fr> wrote:
> Installer sees the partitions of other Linuxes. But when rebooting after
> installation Fedora was the only choice.
>
> Running grub2-mkconfig fixed it, ie other distribution became available.
> Sort of. Problems:
> 1) Fedora was the default and there is no easy way (that is without reading
> the 150+ pages of Grub documentation to change that)
> 2) If user does not know about grub2-mkconfig he will believe he is
> "trapped" in Fedora and will be very, very angry
> 3) Every time he runs the other distribution and updates it he needs to
> rebooot into Fedora and run grub2-mkconfig
Right, I didn't mean to indicate that multiboot on linux doesn't completely
suck, or that linux distros are friendly to each other rather than behaving in
a cannibalistic fashion by default. GRUB2 really isn't meant for mortal users,
just for the members of the lunacy asylum, so this really should work better
than it does yet here we are.
Is this computer by any chance UEFI firmware based? Or is it BIOS? That matters.
On BIOS what's supposed to happen is anaconda calls grub2-mkconfig which in
turn uses os-prober to find other OS's and create something sensible in
grub.cfg. That doesn't always work for various reasons, in particular on UEFI.
What you're probably better off doing, is editing /etc/grub.d/40_custom to add
a very basic entry to locate the CentOS grub.conf. Something like this:
menuentry 'CentOS menu' {
search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt4
--hint-efi=hd0,gpt4 --hint-baremetal=ahci0,gpt4
d7bc9d0e-7706-44f9-b1a7-ff24b7c360a7
legacyconfigfile $prefix/grub.conf
}
Not all hints are needed. Obviously change hd0,gpt4 with the right hint for the
hard drive and partition and partition scheme for where CentOS /boot is
located. The important one, really, is the UUID at the end, which is the file
system UUID for the CentOS boot partition (or rootfs if /boot is a directory on
root). The legacyconfigfile command allows GRUB2 to read legacy GRUB
configuration files. $prefix you should replace with /boot/grub if /boot is a
directory on rootfs or /grub if it's on its own partition.
Now grub2-mkconfig -o /boot/grub2/grub.cfg and this entry will be added to your
Fedora 20 grub.cfg. You'll get an entry that points to the CentOS menu. If you
choose it, the CentOS menu list of kernels should appear. If you want to make
this a default behavior, you'll need to read about $menuentry_id_option for
your CentOS menu entry in the Fedora grub.cfg. By giving it a unique ID, you
can then specify it as the default by that same id in /etc/default/grub.
Yes it's like pulling teeth.
Chris Murphy
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